The invention relates to an apparatus for the fibre-sorting or selection of a fibre bundle comprising textile fibres, especially for combing.
In a known apparatus, fibre material is supplied by means of a supply device to a fibre-sorting device, especially to a combing device, in which clamping devices are provided, which clamp the fibre bundle at a distance from its free end and mechanical means are present which generate a combing action from the clamping site to the free end of the fibre bundle in order to loosen and remove non-clamped constituents, such as, for example, short fibres, neps, dust and the like from the free end, wherein for removal of the combed fibre material a take-off device is present.
In practice, combing machines are used to free cotton fibres or woollen fibres of natural impurities contained therein and to parallelise the fibres of the fibre sliver. For that purpose, a previously prepared fibre bundle is clamped between the jaws of the nipper arrangement so that a certain sub-length of the fibres, known as the “fibre tuft”, projects at the front of the jaws. By means of the combing segments of the rotating combing roller, which segments are filled with needle clothing or toothed clothing, this fibre bundle is combed and thus cleaned. The take-off device usually consists of two counter-rotating rollers, which grip the combed fibre tuft and carry it onwards. The known cotton-combing process is a discontinuous process. During a nipping operation, all assemblies and their drive means and gears are accelerated, decelerated and in some cases reversed again. High nip rates result in high acceleration. Particularly as a result of the kinematics of the nippers, the gear for the nipper movement and the gear for the pilgrim-step movement of the detaching rollers, high acceleration forces come into effect. The forces and stresses that arise increase as the nip rates increase. The known flat combing machine has reached a performance limit with its nip rates, which prevents productivity from being increased. Furthermore, the discontinuous mode of operation causes vibration in the entire machine, which generates dynamic alternating stresses.
EP 1 586 682 A discloses a combing machine in which, for example, eight combing heads operate simultaneously one next to the other. The drive of those combing heads is effected by means of a lateral drive means arranged next to the combing heads having a gear unit which is in driving connection by way of longitudinal shafts with the individual elements of the combing heads. The fibre slivers formed at the individual combing heads are transferred, one next to the other on a conveyor table, to a subsequent drafting system in which they are drafted and then combined to form a common combing machine sliver. The fibre sliver produced in the drafting system is then deposited in a can by means of a funnel wheel (coiler plate). The plurality of combing heads of the combing machine each have a feed device, a pivotally mounted, fixed-position nipper assembly, a rotatably mounted circular comb having a comb segment for combing out the fibre tuft supplied by the nipper assembly, a top comb and a fixed-position detaching device for detaching the combed-out fibre tuft from the nipper assembly. The lap ribbon supplied to the nipper assembly is here fed via a feed cylinder to a detaching roller pair. The fibre tuft protruding from the opened nipper passes onto the rearward end of a combed sliver web or fibre web, whereby it enters the clamping nip of the detaching rollers owing to the forward movement of the detaching rollers. The fibres that are not retained by the retaining force of the lap ribbon, or by the nipper, are detached from the composite of the lap ribbon. During this detaching operation, the fibre tuft is additionally pulled by the needles of a top comb. The top comb combs out the rear part of the detached fibre tuft and also holds back neps, impurities and the like. The top comb, for which in structural terms space is required between the movable nipper assembly and the movable detaching roller, has to be constantly cleaned by having air blown through it. For piercing into and removal from the fibre sliver, the top comb has to be driven. Finally, the cleaning effect at this site of jerky movement is sub-optimal. Owing to the differences in speed between the lap ribbon and the detaching speed of the detaching rollers, the detached fibre tuft is drawn out to a specific length. Following the detaching roller pair is a guide roller pair. During this detaching operation, the leading end of the detached or pulled off fibre bundle is overlapped or doubled with the trailing end of the fibre web. As soon as the detaching operation and the piecing operation have ended, the nipper returns to a rear position in which it is closed and presents the fibre tuft protruding from the nipper to a comb segment of a circular comb for combing out. Before the nipper assembly now returns to its front position again, the detaching rollers and the guide rollers perform a reversing movement, whereby the trailing end of the fibre web is moved backwards by a specific amount. This is required to achieve a necessary overlap for the piecing operation. In this way, a mechanical combing of the fibre material is effected. Disadvantages of that combing machine are especially the large amount of equipment required and the low hourly production rate. There are eight individual combing heads which have in total eight feed devices, eight fixed-position nipper assemblies, eight circular combs with comb segments, eight top combs and eight detaching devices. A particular problem is the discontinuous mode of operation of the combing heads. Additional disadvantages result from large mass accelerations and reversing movements, with the result that high operating speeds are not possible. Finally, the considerable amount of machine vibration results in irregularities in the deposition of the combed sliver. Moreover, the ecartement, that is to say the distance between the nipper lip of the lower nipper plate and the clamping point of the detaching cylinder, is structurally and spatially limited. The rotational speed of the detaching rollers and the guide rollers, which convey the fibre bundles away, is matched to the upstream slow combing process and is limited by this. A further drawback is that each fibre bundle is clamped and conveyed by the detaching roller pair and subsequently by the guide roller pair. The clamping point changes constantly owing to the rotation of the detaching rollers, i.e. there is a constant relative movement between the rollers effecting clamping and the fibre bundle. All fibre bundles have to pass through the one fixed-position detaching roller pair and the one fixed-position guide roller pair in succession, which represents a further considerable limitation of the production speed.